Resistor and method of making



Patented Feb. 5, 1946 RESISTOR AND METHOD OF MAKING Kenneth L. Woodman.Mansfield, Ohio, assig'nor to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvania Application March 27,1943, Serial No. 480,732

13 Claims.

My invention relates, generally, to resistors and it has reference inparticular to a'construction for, and a method of making, resistors ofthe type wherein the resistance element and terminals are secured to asupport by a cementitious insulating material.

Generally stated, it is an object of my invention to provide a multipleterminal imbedded type resistor which is simple and inexpensive tomanufacture and is durable in service.

More specifically, it is an object of my invention to provide forforming a plurality of resistor terminals with an integral connectingportion which serves to space the terminals relative to each other andrelative to the resistor support during assembly.

It is also an object of my invention to provide for protecting theinsulating material by which the resistor element is secured to thesupport.

Still another object of my invention is to provide for imbedding aprotective screen in the insulating material covering a resistanceelement mounted on a metal base.

A further object of my invention is to provide for maintaining apredetermined spacing between a plurality of terminals during themanufacture thereof, and for supporting the terminals in predeterminedrelation to a support by means of a severable common connecting portion.

A further object of my invention is to provide for farming a pluralityof terminals from a com-- mon strip of conducting material and leavingthem connected by an integral connecting portion which may be removedtherefrom after the terminals have been properly secured.

Other objects will in part be obvious, and will in part be explainedhereinafter.

In practicing my invention a plurality of terminals for a resistanceelement which is to be secured to a metal support by a cenientitiousinsulating material are formed from a common sheet of material. Thenormally free ends of the terminals are left connected to a common mentand the portions of the terminals connected thereto. A protective metalscreen positioned over the element is bonded to the support by theinsulating material. When the insulating material hardens, the commonconnecting portion of the terminals may be removed therefrom, leavingthe terminals properly spaced and firmly secured.

For a more complete understanding of the nature and scope of myinvention, reference may be had to the following detailed descriptionwhich may be read in connection with the accompanying drawing, in which:

Figure 1 is a partially broken out plan view of a resistor embodying theprincipal features of the invention:

Fig. 2 is a sectional view taken along the line 11-11 before the commonconnecting portion of the terminals is removed;

Fig. 3 is a plan view of the terminal assembly before the commonconnecting portion is removed;

Fig. 4 is an end elevational view of the terminal assembly of Fig. 3;and

Fig. 5 is a side elevational view of the terminal assembly of Fig. 3.

Referring to Fig. 1 the reference numeral l0 may denote, generally, aresistor of the. type wherein one or more resistance elements Il may besecured to a metal support i2 by means of a cementi'tious insulatingmaterial i3 and provided with one er more sets of terminals (4 foreffecting connection thereto at spaced intervals. A protective screen i5may be provided for protecting the resistor against damage from shock.

Referring to Figs. 1 and 2 it will be seen that the support l2 maycomprise a substantially recvided on the end portions for a purposewhich 4 will be explained hereinafter.

Since the resistance element I l is to be secured to the support II bymeans of the cementitious insulating material [3 and provided with aplurality of relatively closely spaced terminals it, it is necessary toinsure the proper spacing of these terminals during assembly, and beforethey are firmly secured to the base by the insulating material.

Accordingly, as shown in Figs. 2 through 5, the terminals H may beformed in any suitable manner such as by punching or forming them from acommon strip of conducting material. Instead of forming the terminals (4separately, they may be formed with a common connecting strip 28 joiningthe normally free ends. Openings 30 may be provided in the terminalsadjacent the connecting strip for eifecting the connection of aconductor thereto when the resistor is completed, and means such as theupstanding lugs or ears 3'2 may be provided adjacent the other ends ofthe terminals for efiecting a connection to the resistance element.

The terminals may be of any desired shape ha ing, as shonh, in thepresent instance, somewhat of a Z-shape with a substantially ho Zzontalportion adiacent the common connectin strip a substantially verticalintermedia portion adjacent the end to be connected to the resistanceelement. The end to connected to the resistance e ement may be"bstantially pa ailel connection cement as J- bElo generally may havevarious of the invention.

the

el. are relative ng the m....iufac tu"e oi the us may be provi 6. suchas For example, the 23 may be formed ed to engage the are of the ears asno" i i in predetermined relation The feet 2'! may be arranged ncnneing, for example, connected 1G proiectm is of the common connecting bymeans of dependent intermediate ns -16, so as to be positioned in aplane stantially parallel to the ends of the termina s to be connectedto the resistance element 5 i at pre etermined distance below said ends.As shown in 2 this enables the lower ends of the terminals 5 to bepositioned a predetermined distance above the relatively flat backportion E8 of the support, so as to insure adequate insulation beingprovided between the terminals and support.

After the cementitious insulating material l3 has been applied about theresistance element and. the lower ends of the terminals, the connectingportion and the projecting end portions may be severed from theterminals leaving them accurately positioned and ready for use. Where arelatively light material is used for forming the terminals i4 it maynot be necessary to make any particular provision for the severance ofthe connecting portion therefrom, since this may be easily done by means01' shears or punching after the resistor is assembled. If it isdesirable, however, the terminals may be partially severed from theconnecting strip during the origina1 forming operation either bypartially shearing the terminals H from the connecting strip 28 alongthe dotted lines ll or by providing suitable holes at th junction of theterminals and the connecting strip to weaken the union therebetweensufliciently to enable the connecting strip to be readily detached afterthe resistor is assembled.

In order to protect the completed resistor against damage from shock,which may crack the insulating material l3 or even rupture the bondthereof with the support H, the resistor may be provided with aprotective screen IS. The screen l5 may be of any suitable design,comprising a perforated plate of metal or any suitable material havingsufilcient mechanical strength, or a screen, wire mesh or the like. Asshown the shield l5 comprises a screen of cross wires 42 and 43. It maybe secured in any suitable manner being, for example, initiallypositioned relative to the support I! by means of projections 44 of thecross wires 42 which may be retained either by merely bending the ears26 at the ends oi th support thereover or by passing them throughopenings in the cars 26. When the insulating material 13 is flowed overthe resistance element and support, the screen i5 1:" cross imbeddedtherein and may be bonded L0 so as to substantially reinforce theinsulating material and protect the resistance element from damage.

The resistance element may be a se led in any suitable manner, such asby first cing a mery layer of insulating material 5 o er the oe or thesupport 52, bend rminals l4 ment ii -th the er of material s -i as inappiied around stance element ay then be placel on "eccndary r1153projecting 34 in th" 0 26 and bending the cars 25 or tertiary layer ofthen be applied over the protective S01 If the insulating material i3 isof th.

-nings in the ears ,5; further weirdly.

' type the difierent layers may either be fused or partially ifused asthey are applied or they may be left in the uniused state and all fusedsimultaneously in a single heating operation. Likewise, if theinsulating material is of a hydraulic type, the different layers may beallowed to set before the subsequent layer is applied or they may beapplied one after the other and set in a single operation. Whereinsulating materials of the synthetic type are used for hardening bypolymerization it may be desirable to use a single treatment for curingthe different layers in order to permit them to fuse into asubstantially homogeneous mass such as may be secured with the othertypes of insulating materials in either the step by step or thesimultaneous operation.

When the resistance element and terminals are applied to the support,the terminals are accurately positioned relative to one another and tothe support by inserting the bosses 38 on the feet of the projection andportions of the common connecting strip in the openings 2| in the ears20 at the ends of the support 12. I! desired, screws or other suitablemeans may be used to further insure the positioning of the feet 31relative to the cars 20. After the insulating material I! has flowedaround and between the turns of the resistance element the ends of theterminal members and the cross wires of the screen l5 bonding theminseparably together, the common conend secured to the element and theother end necting portion 20 of the terminals, together with theprojecting end portions 28 and the feet Il may be severed from theterminals, leaving them accurately spaced relative to each other and tothe support l2.

From the foregoing description and the accompanying drawing it will beapparent that I have provided in a simple and effective manner forassembling a, plurality of terminals on a resistor of the imbedded type.Accurate positioning of the terminals relative to the resistor supportand to each other is positively assured and removal of the positioningmeans may be easily effected. By protecting the resistance elementthrough the use of a protective shield or screen imbedded in theinsulating material the durability of the imbedded type resistor isgreatly increased. The effective bonding power of the insulatingmaterial is also increased so that the bonding of the terminalsthemselves to the support is thereby improved since cracks in theinsulating material which may develop at points more or less remote fromthe terminals are prevented from separating into the region where theterminals are located.

Since different embodiments of the invention may be made other thanthose illustrated, without departing from the spirit and scope of theinvention as defined, it is intended that all the matter contained inthe accompanying description and shown in the'drawing shall beconsidered as illustrative and not in a limiting sense.

I claim as my invention:

1. A resistor comprising, a relatively flat support, a resistanceelement mounted on said support, a plurality of terminal members havingfeet portions substantially parallel to the support connected to theelementand portions projecting at substantially right angles to thesupport, a cementitious insulating material substantially surroundingthe resistance element and feed portions and securing them to thesupport.

2. A resistor comprising, a metal base, a resistance element positionedon the base, a plurality of contact members having portions insubstantially the plane of the element secured thereto at projectingtherefrom in a plane parallel to but spaced from the plane of the endsecured to the element, and a fusible cementitious insulatin materialpositioned about the element and the ends of the terminals securedthereto fusibly bonding them to the base.

.6. A resistor comprising, a substantially flat metal tray havingupstanding edges, a resistance element positioned in the tray, aplurality of elongated sheet metal terminals arranged in spaced relationadjacent one edge of the tray and having terminal portions projecting atan angle to the tray and feet portion in substantially parallel relationto the tray secured to the resistance element at spaced intervals.

7. A multiple terminal assembly comprising, a

. plurality of spaced terminal members formed spaced intervals andangularly related portions projecting away from the base, a cementitiousinsulating material surrounding the resistance element and the firstmentioned portions of the contact members to secure them to and insulatethem from the base.

3. A resistor comprising, a resistance element having projectingterminals, 9. metal support positioned on one side of the element and inspaced relation thereto, a metal screen positioned on the other side ofthe element in spaced relation, and a fusible cementitious insulatingmaterial substantially surrounding the -element fusibly bonded to thescreen and support.

4. A resistor comprising, a relatively flat metal support havingupstanding edge portions, a resistance element positioned inpredetermined spaced relation to the support, a shield positioned on-the side of the element remote from the support and operativelyconnected to the edge portions of the support, and a vitreous insulatingmaterial substantially surrounding the element and fusibly bonding it tothe support and shield.

5. A resistor comprising, a substantially rectangular base havingsupporting ears at each end and upturned side portions, a resistanceelement supported on the base having a. plurality of elongated terminalmembers positioned at spaced intervals adjacent one edge of the basehaving one from sheet metal, removable connecting means integrallyformed with the terminal members to maintain a predetermined spacingthereof during assembly, and positioning means projecting from theconnecting means adjacent the ends integral with the connecting meanshaving a portion thereof in predetermined relation to portions of theterminals for positioning them in predetermined relation to a supportduring assembly.

8. A terminal structure for a resistance elemen mounted on a supportcomprising, a plurality of elongated sheet metal terminal members havingmeans at one end for connection to a conductor, and a severableconnecting strip connecting the other ends to maintaining the terminalmembers in predetermined alinement and spaced relation during assemblyand having integral depending end portions projecting from theconnecting strip for positioning the terminal members relative to thesupport during assembly.

9. The method of making a resistor having a plurality of terminalsconnected to a resistance element which comprises, forming the pluralityof terminal members from a single piece of conducting material having aseverable connecting. portion along one end, securing the other ends tothe resistance element and applying the resistance element and terminalsto a support, applying a cementitious insulating material over theelement. and at least a portion of the terminals to bond them to thesupport, and removing the common connecting portion from the free endsof the terminals.

10. The method of making a multiple terminal resistor which comprises,forming a plurality of spaced terminals from a piece of conductingmaterial having means at one end to make connection to a resistanceelement and having an integral' connecting strip at the other,connecting the first-mentioned ends to the resistance element applyingthe terminals and element to a support, surrounding the element and thefirst-mentioned end portions of the terminals with a cementitiousinsulating material, and severing the connecting portion from the otherends of the terminals when the insulating materialhardens.

11. The method of alining a plurality of spaced terminals for connectionto a conductor which comprises forming the terminals from a common pieceof conducting material in predetermined spaced relation with means foreffecting connection to the conductor at one end and a severable spacingand connecting strip integral therewith at the other, connecting theterminals to the conductor and securing them in the desired relationthereto, and then severing the connecting strip therefrom.

12. The method of making a resistor having a plurality of spacedterminals connected to a resistance element imbedded in a vitreousenamel on a metalsupport which comprises, forming the terminals in thedesired spaced relation from a common sheet of conducting material withspaced ears at one end to grip the resistance element and a commonconnecting portion at the other with projecting end portions positionedin predetermined relation to the ends having the spaced ears, applyingthe terminals to the element, applying the element and terminals to thesupport with the projecting end portions supporting the terminalsrelative to the support, applying a oementitious insulating materialabout the element and the portions of the terminals secured thereto, andremoving the connecting portion and projecting end portions from theterminal portions. 2

13. The method of makinga multiple terminal resistor which comprises,forming a plurality of spaced terminals from a common sheet ofconducting material with a common connecting portion at one end andprojecting ears at the other end for gripping a resistance element,securing the terminals to the resistance element while spaced by thecommon connecting portion, positioning the element and terminals on ametal base having a layer of cementitious insulating material thereon,covering the element and the ends of the terminals secured thereto withadditional cementitious insulating material, placing a protective screenover the element and securing it to the base, treating the cementitiousmaterial to bond with the base, resistance element and protectivescreen, and subsequently removing the common connecting portion.

KENNETH L. WOODMAN.

